In the following, take C_v = 35.4 and Cp = 44.5 J mol^-1 degree C^-1 for carbon

Question

In the following, take C_v = 35.4 and Cp = 44.5 J mol^-1 degree C^-1 for carbon disulfide gas: Five moles of carbon disulfide at 25 degree C, contained in a rigid vessel, is heated to 265 degree C. How much head is required if the vessel has a negligible heat capacity? If the vessel weighs 100 kg and has a heat capacity of 0.5 kJ kg^-1 degree C^-1, how much heat is required? 264 g of carbon disulfide at 300 degree C is contained in a piston/cylinder arrangement. How much heat must be extracted from this system, which is kept at constant pressure, to cool it to 50 degree C if the heat capacity of the piston and cylinder is neglected?

Explanation / Answer

a) since the heating is done in rigid vessel,

V is constant

so Cv will be used

heat required = n*Cv*(dT)

= 5 * 35.4*(265-25)

= 42480 J = 42.48 kJ

if vessel has heat capacity of 0.5

then heat required = 42.48 kJ + 0.5 * 100 * (265-25) kj

= 42.48 + 50*240

= 12042 kJ

b) constant pressure , cp will be used

molar mass of carbon disulphide = 76.139

so number of moles = 264/76.139 = 3.4673

heat required for extraction = 3.4673 *44.5*(300-50) =38574.18668 J

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